Bad_mojo said:
Hi,
FWIW two drivers increase sensitivity and maximum levels.
You not get any more bass extension than the single case.
The Peerless 8" gives the most bass extension.
🙂/sreten.
sreten said:
Sreten, in a TMM 2.5 way, the second woofer share the "load" for reproducing the lower end... to me that means a possibility for a little more base...
Look at bellow 200hz, http://zaphaudio.com/WaveguideTMM-perfection-FR-woofers-individual.gif both woofers share 50/50. That to me looks like a boos in the low end... even if part of the goal is also to share the load by two driver to reduce excursion... distortion... It can still allow for some gain in the low end.
Granted maybe not as much gain as with an 8" but I don't know... Maybe mids are better on a 7" TMM??? Is it worth pursuing a TMM 7" over a TM 8"???? If you haven't built both, or don't backup your statements I might not believe you. LOL
Mo
sreten is right. Using two identical woofers does not extend bass but only increase power handling. A .5 woofer in a TMM should be viewed as a means of baffle step compensation (in this case full BSC). You can achieve the same amount of BSC and as a result the same frequency response in MTM.
As for the vertical lobing error of MTM, I wouldn't worry. This should not be an important consideration unless your ear level often changes from listening to listening or the speaker is used horizontally as a CC. Some people even think too wide a vertical listening window is not good due to room interaction. Linkwitz-Riley 2nd order 2-way designs often have narrow vertical lobes, which is even preferred by some people.
As for the vertical lobing error of MTM, I wouldn't worry. This should not be an important consideration unless your ear level often changes from listening to listening or the speaker is used horizontally as a CC. Some people even think too wide a vertical listening window is not good due to room interaction. Linkwitz-Riley 2nd order 2-way designs often have narrow vertical lobes, which is even preferred by some people.
Bad_mojo said:
???
I'm stating very basic stuff I have no intention of "backing up".
For comparing doubled bass drivers the assumption is the box
is double the volume and the bass alignment is exactly the same.
Excursion / distortion levels are not bass extension.
This is F-3dB, F-6dB and F-9dB of the bass alignment.
If you do not know I've stated something wrong do not suggest
I have, you will generally find a misunderstanding of the precise
meaning of something on your part.
🙂/sreten.
sreten said:
Sreten, get off your high horse man and relax... Maybe I'd like to hear from someone else? Will your highness allow such a request? (Mo is bowing as he is requesting)
Mo
Jay_WJ said:
He he I guess he was right! LOL
That is what I don't understand... In an MTM, the lobing will happen between the two woofer below the X-over region, and in the x-over region it will cause between the tweeter AND the woofers, Above the x-over region, the tweeter runs unaffected so no lobing above 3000hz...
Doesn't that affect things in a "weird" way to have everything bellow 3000hz lobed and everything above running in a wide/tall dispersion? Just doesn't seam "thorough" to me at least.
Mo
LR2 or LR4, TM or MTM, drivers' natural rolloffs (or beaming), xover point, etc all cause different power responses across systems. The question is, what kind of power response is better? It's a tough question, and should also depend on personal preference.
Take a look at this page about power responses of LR2 vs LR4:
http://www.rjbaudio.com/Audiofiles/LR power response.html
LR2 has a wider dip around the xo point due to wider nulls in the lobing patterns (i.e., narrower vertical listening window) than LR4. Which is better? It depends on other factors (as said above), and also on personal taste.
Edit: The reason why a narrow vertical lobe is often preferred by some people is that the frequency range where this lobing occurs is often the range to which human ears are very sensitive. Room interaction due to ceiling and floor reflection may be more obtrusive in this frequency range. And as you may know, higher frequency sound is easily absorbed even by untreated drywalls.
Take a look at this page about power responses of LR2 vs LR4:
http://www.rjbaudio.com/Audiofiles/LR power response.html
LR2 has a wider dip around the xo point due to wider nulls in the lobing patterns (i.e., narrower vertical listening window) than LR4. Which is better? It depends on other factors (as said above), and also on personal taste.
Edit: The reason why a narrow vertical lobe is often preferred by some people is that the frequency range where this lobing occurs is often the range to which human ears are very sensitive. Room interaction due to ceiling and floor reflection may be more obtrusive in this frequency range. And as you may know, higher frequency sound is easily absorbed even by untreated drywalls.
Jay_WJ said:
Still trying to digest what you just said but I am choking on something.... What is the difference between a power responses and frequency responses. I read what RJB wrote but I still don't get it. Anyone want to take a stab at it? I always assumed that LR x-overs had a flat response????
For higher frequencies, I always thought you could prevent them from annoying your neighbors with simply doubling the drywall thickness... but they are easily reflected back to the listener no??? Like when a high pitched alarm goes off when a jewelry store clerk is trying to show you something and he accidentally triggers the alarm. I can never know where it is coming from, feels like it's coming from everywhere.
Mo
Lobing Concerns
All I can say is, the proof of the pud is in the eating.
I hear nothing remotely weird!
I squeezed the drivers close together with the tweeter offset a bit and the surrounds just touching, so they are close. And I listen with ears at tweeter height.
Sounds *fine*!
Don't worry about non problems ...
Rgds
Mike
Bad_mojo said:
All I can say is, the proof of the pud is in the eating.
I hear nothing remotely weird!
I squeezed the drivers close together with the tweeter offset a bit and the surrounds just touching, so they are close. And I listen with ears at tweeter height.
Sounds *fine*!
Don't worry about non problems ...
Rgds
Mike
Bad_mojo said:
A power response is an average concept---average of off-axis responses at different angles, and when we say a speaker has a flat frequency response, we usually mean its on-axis response. LR type xovers have flat on-axis response. LR2, LR4, BW1, and BW3 xovers all have a flat on-axis response but their power responses are all different.
What I meant by "higher frequency" is above several kHz, which is easily absorbed by most types of wall, carpet, and a thin layer of cloth. A high pitched alarm you're talking about is far below this range.
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